1. Field of the Invention
The present invention relates to a dual-fuel injector which allows precise control of liquid and slurry fuel injection into an engine or the like. More particularly, the present invention relates to an electronically actuated injector which uses pressurized liquid fuel to operate respective liquid and slurry fuel assemblies, which prevents separation of solid material from the liquid carrier in the slurry fuel, and which prevents abrasion of injector surfaces by the solid material.
2. Description of the Prior Art
It is known in the prior art that a pulverized solid fuel material slurried in a liquid carrier can be made to combust in an engine such as a diesel engine. For example, coal slurried in a water carrier can be made to combust in a diesel engine to provide operating power thereto. A typical slurry fuel, however, will not ignite under pressure alone but requires ignition by another source such as conventional diesel fuel.
The technical problems concerning slurry fuel injection have heretofore prevented development of a practical injection system. For example, the ignition timing of a liquid fuel in relation to the timing of slurry fuel injection is critical in order for the solid fuel material to ignite and efficiently burn.
Additionally, the slurry fuel itself presents problems. For example, a solid fuel material such as coal has a tendency to separate from the liquid carrier. When this occurs, the solid material tends to accumulate within the injector rendering it inoperable. Also, a solid material such as coal tends to accumulate adjacent moving surfaces in an injector and quickly abrades and corrodes these surfaces.
Furthermore, known prior art fuel injection systems for liquid and slurry fuels use separate injectors which increase the mechanical complexity of the system, and use mechanically operated slurry fuel injectors which require coupling with the cam shaft of the engine. This prevents effective "on-the-go" adjustment of the injection timing at different engine operating speeds.